In known sailboard constructions a generally horizontal, aftward-extending boom is lashed to the upright mast. The head of the generally triangular fore-and-aft sail is connected to the tip of the mast such as by a pocket of the sail head being fitted over the mast tip. The clew of the sail is connected to the aft end of the boom by the outhaul. The tack of the sail is connected to the foot of the boom by the downhaul. Sometimes the connection of the head of the sail to the mast can be adjusted during rigging to accommodate masts of different heights. Prior to sailing, the outhaul tension and the downhaul tension are set. None of these adjustments is altered during sailing.
Sophisticated and expensive sailboard sails have been designed to change shape in differing wind conditions. For example, different sail materials can be used in different parts of the sail to stretch differently depending on wind direction and strength. In addition, sailboard sails have been designed to take advantage of the inevitable structural changes due to dynamic loading while sailing, such as changes in mast curvature. Still, the shape of the sail airfoil has been predetermined at the time of rigging and there is no known mechanism permitting changes while under sail.